Using the compressed and extended lengths taken from existing shocks may not be the most accurate for your vehicle. Set the vehicle at the desired ride height and measure from the center of the upper shock mount to the center of the lower shock mount to determine the length of shock needed. This method of measuring shock lengths works with both coil-over and non coil-over applications. If a measurement should fall between shock lengths, choose the shock that gives you the most compression (in) travel.